Although　there　are　numerous　experimental　studies　of　the　size　effect　on　nominal　splitting　tensile　strength　of　concrete　materials　being　performed,　research　on　effect　of　specific　material　parameters　involving　maximum　aggregate　size　(MAS)　and　concrete　strength　grade　(CSG)　on　the　splitting　tensile　strength　of　concrete　materials　is　relatively　rare.　This　paper　investigated　the　influence　of　MAS　and　CSG　on　macro　splitting　tensile　behavior　of　concrete　materials　and　the　corresponding　size　effect　from　both　experimental　and　numerical　perspectives.　Four　groups　of　maximum　aggregate　sizes　(10,　20,　30,　and　40　mm)　and　three　groups　of　concrete　strength　grades　(C20,　C40,　and　C60)　were　considered,　and　a　total　of　84　concrete　cubic　specimens　with　different　side　lengths　(150-350　mm)　were　tested.　A　three-dimensional　mesoscale　numerical　method　was　established　and　a　total　of　114　concrete　cubic　models　(with　side　length　up　to　600　mm)　with　different　MAS　and　CSGs　were　simulated.　The　results　indicate　that　splitting　tensile　strength　decreases　with　increasing　side　length　and　the　downtrend　of　strength　decreases　as　side　length　increases.　The　downtrend　of　strength　in　concrete　specimens　with　smaller　MAS　was　more　obvious,　and　the　increase　in　MAS　can　reduce　the　sensitivity　to　the　size　effect　on　the　splitting　tensile　strength.　Concrete　specimens　with　higher　strength　grades　had　more　obvious　downtrends　of　strength　than　did　specimens　with　lower　strength　grades.　The　influential　mechanism　of　MAS　and　CSG　on　the　macroscopic　failure　behavior　and　the　corresponding　size　effect　of　concrete　materials　were　analyzed　preliminarily.